Data-Over-Cable Service Interface Specifications (“DOCSIS”) has been established by cable television network operators to facilitate transporting data traffic, primarily internet traffic, over existing community antenna television (“CATV”) networks. In addition to transporting data traffic as well as television content signals over a CATV network, multiple services operators (“MSO”) also use their CATV network infrastructure for carrying voice, video on demand (“VoD”) and video conferencing traffic signals, among other types.
An MSO may use what is known in the art as PacketCable for providing telephony services to users. PacketCable™, which is a trademark of CableLabs®, facilitates the presentation of a transparent interface to a user with respect to operation of the network. In other words, a user plugs a standard telephone into a user device, which presents to the telephone what appears to be a traditional plain old telephony service (“POTS”) line card interface. However, the user device transforms analog POTS signals to and from the telephone from/to internet packets.
Such a user device typically includes a media terminal adaptor (“MTA”) that performs processing of signals between the telephone and the network interface portions of the user device. When a user device, such as one containing an MTA, performs processing of telephony signals for transport over a network according to PacketCable, secure provisioning of the MTA device is performed according to procedures set forth in the PacketCable specification. Such secure provisioning ensures that the device securely receives information that allows it to confirm with the network that it is the device it purports to be. Transporting of the user device configuration data as specified in the PacketCable specification is typically performed securely according to protocols and procedures that prevent unauthorized access to information related to the user device and associated user.
Similarly, DOCSIS has a method for confirming that information purporting to be from the cable modem is in fact from the cable modem. Both PacketCable and DOCSIS use certificates issued by certificate authorities.
As known in the art, a certificate authority (“CA”) issues a certificate that binds a public key to other information, including the name of the entity that owns the certificate and the public key. Thus, if a receiving entity receives data that is signed by a sender entity along with the sender entity's certificate, and the receiving entity is in possession and trusts the certificate authority chain that has signed the sender entity certificate, then the receiving entity can trust that the data is from the sending entity that is named in the certificate.
However, if the certificate authority is compromised, such as would occur if security procedures were not followed properly, then all the issued certificates under the certificate authority hierarchy up to the compromised certificate authority become invalid. Therefore the receiving entity can no longer trust the sender entity certificate or its signature. When the number of certificates under a compromised CA is limited, such as a web server CA that issues a limited number of certificates to its web site servers, the certificate authority can typically recover easily. By reissuing the compromised CA certificates in the hierarchy and the end entity certificates, the operator can manually and securely re-provision the new end entity certificates and keys on each compromised unit.
The solution may not be so easy, however, in the case where hundreds of thousands, if not millions, of devices each need their own certificate. Such an example may be cable modem and MTA devices, or digital subscriber line (“DSL”) modems used by subscribers at their homes and/or offices. The solution is not simple or easy because the public key contained in a certificate is associated with a private key embedded in the device to which the certificate corresponds. The private keys are typically embedded into the device's memory, such as nonvolatile memory, when the device is manufactured. Thus, to install new certificates and keys securely to each of the large number of subscriber devices could require return of each of the thousands or millions of devices to the manufacturer.
Therefore, there is a need in the art for a method and system for distributing new device certificates to a plurality of subscriber devices without the need for physically returning the devices to a manufacturing location for replacement of the devices' certificates and private key(s)